/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.stdlib.statistics.function;

import axil.api.AxilObject;
import axil.api.extend.Environment;
import axil.api.extend.Function;
import axil.api.extend.Parameters;
import axil.api.extend.Source;
import axil.stdlib.numbers.type.Int;
import axil.stdlib.numbers.type.Num;

import java.util.ArrayList;

import static axil.framework.Functions.iter;
import static axil.framework.Functions.num;

/**
 * The standard evaluation for statistical functions that perform a complex calculation on a list.
 */
public abstract class ComplexListCalculation implements Function {
    /**
     * Execute the specific statistical function against the given arguments.
     */
    protected abstract AxilObject calculate(ArrayList<Num> values);

    /**
     * This is the result that should be returned if nothing is passed to the function;
     * if the parameter size is zero. The default is to return zero.  Some may choose to return Nil.
     */
    protected AxilObject zeroResult()
    {
        return Int.zero;
    }

    /**
    * Execute this function with the given arguments. The Axil compiler will
    * ensure that the number of arguments passed to the function are valid.
    * If this function fails during execution for any reason, then an exception
    * is thrown.
    */
    public AxilObject eval(Environment env, Parameters params, Source source) {
        final int size = params.size();
        switch(size) {
            case 0:
                return zeroResult();

            case 1:
                // A single list (containing values) was passed.
                AxilObject a = params.a();
                if (a instanceof Iterable) {
                    ArrayList<Num> values = new ArrayList<Num>();
                    for (AxilObject obj : iter(a)) {
                        values.add(num(obj));
                    }
                    return calculate(values);
                }
                return a;

            default:
                // a list of values was passed.
                ArrayList<Num> values = new ArrayList<Num>(size);
                for (int i = 0; i < size; i++) {
                    values.add(num(params.at(i)));
                }
                return calculate(values);
        }
    }
}
